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Coating Process with Improved Extrusion Arrangement Disclosure Number: IPCOM000009574D
Publication Date: 2002-Sep-04
Document File: 6 page(s) / 35K

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The Prior Art Database


A manufacturing method for mechanical closure systems for disposable diapers which uses a hotmelt coating process for providing laminates is disclosed. A problems with known solutions is that when stopping the web movement, the extrusion head will burn through the web due to overheating of the material. On the other hand, the web will have a certain forward feed when the web is completely stopped because of the inertia of masses in movement . While re-starting the web movement, an uncoated web area is obtained due to the forward feed. The Coating Process with Improved Extrusion Arrangement overcomes these problems with a movable arrangement of the extrusion head. The extrusion head will be elevated when stopping the web, and as a result no overheating will occur due to the larger distance of the extrusion head to the immobile web. Also, the extrusion head is moved along the distance of the forward feed described, exactly to the point, where the coated area ends. Long process interruptions due to burn through of the web as well as waste of web material (uncoated area) will be avoided with the improved method described above.

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Coating Process with Improved Extrusion Arrangement

Nowadays diapers are disposable products and therefore the diaper must be low cost and easy to use. The diaper includes mechanisms for fastening and fixing it in the right way to keep it tight. For this purpose, closure systems such as mechanical fasteners are used.

Mechanical fasteners are generally two-component systems such as hooks and loops and these fasteners much be attached securely to the diaper body to ensure the closing function. It is important that the connection of the mechanical fasteners to the diaper body forms an inseparable bond.� Insufficient bond or improper bonding could result in damage to the diaper body surface and/or a loss of closing function.

A common method of attaching the mechanical fasteners to the diaper body is through the use of pressure-sensitive adhesives (PSAs).� The use of hot melt adhesives is a well known and commonly employed technology.�

To manufacture loop tape it is necessary to apply a PSA to the backside of the loop material (side opposite the loop surface). An application device comprising an extrusion head is commonly installed just above the moved the web of loop material in order to apply a coating of hot melt PSA.

One problem encountered during the extrusion process is that when starting or stopping the moving web, the amount of heat released to the web material is too high. During the coating process only a certain short time of heat impact to the web material is allowed due to its thermo-sensitivity.� If the time is too long, overheating of the web material and melting through can result. When starting the movement of the web again a certain length of the web can will remain uncoated. These problems increase the costs for producing coated web and diapers due to the waste of material mentioned.

To avoid these difficulties it is suggested to have an improved coating arrangement with a movable extrusion head.

The function of such improved arrangement can be described as follows. There is a two-directional movement of the coating head; horizontally and vertically. This means that the head will not only be moved over a certain distance downweb, but also with a changing distance to the web. Both movements happen successively, so that there will be in a first step the up or down movement; and in a second step, there will be the movement horizontally or downweb.

One benefit of vertical movement of the coating arrangement is that there will not be any melting through the web in the case of starting or stopping the web as described above. At the moment of stopping the web movement, the coating head arrangement will be lifted to a higher distance from the web and so the impact of heat to the web material will be much lower.� This vertical movement can result in uncoated web material as the PSA has not reached the web during the stopping phase.

These uncoated zones come from the fact that there will be some delay in the stopping of the web. As a resu...